import Vue from 'vue';

Vue.directive('dialogDrag', { //属性名称dialogDrag，前面加v- 使用

    bind (el, binding, vnode, oldVnode) {

        const dialogHeaderEl = el.querySelector('.el-dialog__header');

        const dragDom = el.querySelector('.el-dialog');

        //dialogHeaderEl.style.cursor = 'move';

        dialogHeaderEl.style.cssText += ';cursor:move;'

        dragDom.style.cssText += ';top:0px;'

        // 获取原有属性 ie dom元素.currentStyle 火狐谷歌 window.getComputedStyle(dom元素, null);

        const sty = (function () {

            if (window.document.currentStyle) {

                return (dom, attr) => dom.currentStyle[attr];

            } else {

                return (dom, attr) => getComputedStyle(dom, false)[attr];

            }

        })()

        dialogHeaderEl.onmousedown = (e) => {

            // 鼠标按下，计算当前元素距离可视区的距离

            const disX = e.clientX - dialogHeaderEl.offsetLeft;

            const disY = e.clientY - dialogHeaderEl.offsetTop;

            const screenWidth = document.body.clientWidth; // body当前宽度

            const screenHeight = document.documentElement.clientHeight; // 可见区域高度(应为body高度，可某些环境下无法获取)

            const dragDomWidth = dragDom.offsetWidth; // 对话框宽度

            const dragDomheight = dragDom.offsetHeight; // 对话框高度

            const minDragDomLeft = dragDom.offsetLeft;

            const maxDragDomLeft = screenWidth - dragDom.offsetLeft - dragDomWidth;

            const minDragDomTop = dragDom.offsetTop;

            const maxDragDomTop = screenHeight - dragDom.offsetTop - dragDomheight;

            // 获取到的值带px 正则匹配替换

            let styL = sty(dragDom, 'left');

            let styT = sty(dragDom, 'top');

            // 注意在ie中 第一次获取到的值为组件自带50% 移动之后赋值为px

            if (styL.includes('%')) {

                styL = +document.body.clientWidth * (+styL.replace(/\%/g, '') / 100);

                styT = +document.body.clientHeight * (+styT.replace(/\%/g, '') / 100);

            } else {

                styL = +styL.replace(/\px/g, '');

                styT = +styT.replace(/\px/g, '');

            };

            document.onmousemove = function (e) {

                // 通过事件委托，计算移动的距离

                let left = e.clientX - disX;

                let top = e.clientY - disY;

                // 边界处理

                if (-(left) > minDragDomLeft) {

                    left = -(minDragDomLeft);

                } else if (left > maxDragDomLeft) {

                    left = maxDragDomLeft;

                }

                if (-(top) > minDragDomTop) {

                    top = -(minDragDomTop);

                } else if (top > maxDragDomTop) {

                    top = maxDragDomTop;

                }

                // 移动当前元素

                dragDom.style.cssText += `;left:${left + styL}px;top:${top + styT}px;`;

            };

            document.onmouseup = function (e) {

                document.onmousemove = null;

                document.onmouseup = null;

            };

        }

    }

})